Many reactions require high temperatures and pressures to take place and are therefore carried out in a reactor. As a result, reactors typically have an outer pressure vessel for withstanding the pressure in the reactor. A dual vessel reactor has an inner vessel in which the reaction may be carried out. The inner vessel is heated to a reaction temperature either by an external source or by the reaction itself. The outer vessel is typically a pressure vessel and has a relatively large thickness as compared to the inner vessel wall so that the reactor can handle elevated reaction pressures.
Some chemical reactions, for example, the devulcanization of rubber, require temperatures as high as 350° C. As a result, a door in the outer vessel requires that a metal ring be used to seal the door with the reactor when in the closed position. A rubber seal cannot be used as the high temperatures of the reactor and specifically the outer vessel damage the seal and can cause failure of the seal which is costly and creates safety issues when the pressure can no longer be contained.
Metal seals, such as metal American Petroleum Institute (API) rings, are costly, can only be used once, and therefore drive up the cost of running a reaction in a reactor. Furthermore, reactors having outer vessels that experience higher operating temperatures, experience higher rates of corrosion on the metals used in the outer vessel and therefore require the use of costly metals such as stainless steel or other equivalent costly alloys in fabrication. Any increase in temperature of the outer vessel increases the corrosion rate. Furthermore, conventional coatings, such as paints, that can be used to protect steel at elevated temperatures are difficult to find.
Water cooling the seal is a possibility, and water cooled seals are available. However water cooling the large metal flange which houses the seal will result in the flange operating at lower temperatures and as a consequence will cause a substantial amount of condensation onto it, and heat transfer to it. Ignoring for a minute the costs associated with this heat loss, such a loss of heat will ultimately limit the operating temperature of the reactor, that is, the heat that is being added to heat the vessel is being lost through condensation on the flange. As a result, water cooling the seal is undesirable.
A need therefore exists for a dual vessel reactor for use in reactions having a high reaction temperature, having an outer vessel suitable for operation with a non-metal seal and a method of carrying out a reaction in a reactor wherein the outer vessel of the reactor does not exceed an operating temperature of a non-metal seal or has an operating temperature lower than the reaction temperature.